Varicella Cases Research Articles

A randomized trial assessing the efficacy, immunogenicity, and safety of vaccination with live attenuated varicella zoster virus-containing vaccines: ten-year follow-up in Russian children

ABSTRACT In Russia, a universal varicella vaccination (UVV) program has not been implemented, and varicella vaccination coverage is low. We assessed the efficacy, antibody persistence, and safety of one- and two-dose varicella vaccination schedules in Russian children with a ten-year follow-up period, as part of an international phase IIIB, observer-blind, randomized, controlled trial (NCT00226499). Children aged 12–22 months were randomized (3:3:1) to receive two doses of tetravalent measles-mumps-rubella-varicella vaccine (V2 group), one dose trivalent measles-mumps-rubella (MMR) vaccine and one dose of varicella vaccine (V1 group), or two doses of MMR vaccine (V0 [control] group), 42 days apart. Main study outcomes were: vaccine efficacy (VE) against confirmed varicella cases, anti-varicella zoster virus (VZV) seropositivity rates and geometric mean concentrations, and reporting of (serious) adverse events ([S]AEs). The total vaccinated cohort in Russia comprised 1000 children; 900 were followed up until study end (year [Y] 10). VE estimates against confirmed varicella (Y10) were 92.4% in the V2 group and 74.7% in the V1 group. Anti-VZV seropositivity rates remained ≥99.4% in the V2 group and ≥89.7% in the V1 group from day 42 post-vaccination 2 until Y10. Occurrence of (un)solicited AEs and SAEs was similar across groups and confirmed the safety profile of the vaccines. No vaccination-related SAEs or deaths were reported. These results are consistent with the global trial results, i.e., the highest VE estimates observed following the two-dose schedule compared to the one-dose schedule. These data may inform decision-making related to potential implementation of a UVV program.

Health technology assessment of varicella vaccine in the Armed Forces

BackgroundThe Indian Armed Forces, on entry, vaccinates all cadets and recruits with varicella vaccine for the prevention of varicella. This health technology assessment (HTA) report puts forth evidence for HTA of varicella vaccination in the Armed Forces in various domains namely clinical, societal, ethical, economic, and legal. MethodsThe policy question under each domain has been developed according to best-practice methods for HTA. The costs included were hospitalization cost due to varicella infection; training lost cost; the varicella vaccine cost; cost of the side effects of vaccine; and the outbreak investigation cost. The incremental cost-effectiveness ratio (ICER) for varicella cases averted and man-days saved, and quality-adjusted life years (QALYs) gained due to varicella vaccination strategy were calculated. ResultsEvidence suggests a reduction of 81% in hospitalization rates with 19392 man-days saved per 1 lakh population due to varicella vaccination strategy. The ICER for varicella cases averted is estimated to be Rs 56732/- per case averted and Rs 5687/- per man-day saved. QALYs gained due to two-dose varicella vaccination strategy is estimated to be 1152 per 1 lakh population with cost per QALY gained Rs 95735/-. ConclusionThe study showed a large reduction in hospitalizations and consequently man-days lost after the introduction of the vaccination strategy. The QALYs was another aspect of importance brought out by this study. Thus, a two-dose vaccination strategy for varicella-zoster virus (VZV) for the Armed Forces trainees is a cost-effective policy.

Severe chickenpox disease and seroprevalence in Sweden – implications for general vaccination

Objectives: To describe the current panorama of severe chickenpox disease and seroprevalence in Sweden, as a basis for the approaching decision on universal vaccination.Methods: Patients discharged with an International Classificationof Diseases 10th revision-code for chickenpox (B01-B01.9) in eight pediatric and infectious diseases departments in Stockholm and Gothenburg in 2012-2014 were included in the study and their medical charts were reviewed. Further, residual serum samples collected from 11 laboratories across Sweden were analyzed for varicella zoster IgG-antibodies to investigate age-specific seroprevalence.Results: A total of 218 children and 46 adults were included in this hospital-based study; 87.2% of children and 63.0% of adults had complications. An underlying condition was not associated with an increased risk of complication. Dehydration (31.7%), bacterial skin infections (29.8%) and neurological involvement (20.6%) were the most frequent complications in children. Among adult cases, 63% were born abroad. The seroepidemiological analysis included 957 patient samples. Seroprevalence was 66.7% at 5 years and 91.5% at 12 years. Infants and adolescents/adults were overrepresented among admitted patients compared to seroprevalence data.Conclusions: Half of all complications in hospitalized chickenpox cases were seen in previously healthy children, which supports universal childhood vaccination. Adult migrants was a risk group for chickenpox hospitalization. Age-specific seroprevalence was similar to neighboring countries.

Economic evaluation of varicella vaccination strategies in Jiangsu province, China: a decision-tree Markov model

ABSTRACT This study evaluated different varicella vaccination strategies in Jiangsu province, China. A decision-tree Markov model was used to evaluate the cost effectiveness of various varicella vaccination strategies for children, including direct and selective vaccination (serotesting pre-vaccination). A cohort of one-year-old children was followed through 60 one-year Markov cycles. The parameter estimation was based on field work, the literature, and statistical yearbooks. We calculated the incremental cost-utility ratio (ICUR) using the saved quality-adjusted life year (QALY). One-way and probability sensitivity analyses were performed to assess uncertainty. Among 100,000 cohort members, one-dose and two-dose direct vaccination averted 8061 and 10,701 varicella cases, respectively, compared with no vaccination. Furthermore, compared with no vaccination, one-dose and two-dose direct vaccination saved one QALY at the ICUR of USD 21,401.33 and USD 35,420.81, respectively, at less than three times the per capita gross domestic product (USD 47,626.86) of Jiangsu. The ICURs of the one-dose and two-dose selective strategies versus no vaccination were USD 42,623.62 and USD 51,406.35 per QALY gained, respectively. The cost effectiveness results were most sensitive to the QALY loss of outpatients and vaccine prices. Thus, in Jiangsu, one-dose and two-dose direct varicella vaccination in children could be cost effective at the willingness to pay threshold of three times provincial GDP per capita from a societal perspective. The findings were sensitive to the vaccine price and health utility of varicella cases.

Reducing Effects of Anti-Epidemic (Quarantine) Measures during the COVID-19 Pandemic on the Incidence and Spread of Airborne Infectious Diseases (Based on the Example of Varicella)

Background. The coronavirus pandemic, also known as the COVID-19 pandemic, introduced significant changes in vital activities of the population and spread of airborne infectious diseases, the study of which enables ranking of preventive measures. The objective of our study was to assess the degree of influence of the lockdown and social distancing imposed in the Krasnodar Krai in 2020 due to the pandemic on the incidence of airborne communicable diseases based on the example of varicella. Materials and methods. We conducted a retrospective analysis of a 10-year incidence of varicella in the population of the Tuapse district, Krasnodar Krai using monthly and annual data on the incidence of infectious and parasitic diseases (Form No. 2) in the Tuapse district for 2011–2020 and the “Population Incidence” software, version 5, by applying standard techniques and methods of studying the epidemic process. Results. Stringent restrictive measures taken in the country in 2020 in the context of the COVID-19 pandemic caused a significant decrease (by 741 %) in the incidence of chickenpox among the population of the Tuapse district compared to the long-term average rate. In April – May and July – September 2020, varicella incidence rates were 30.98 and 7.75 per 100 thousand population or 7.4 and 18.8 times lower than the long-term average, respectively. The majority of chickenpox cases in the Tuapse district (as in the country as a whole) were pediatric – 94.02 % (RF – 94.3 %), with children aged 3 to 6 years making up 61 % of the total. Conclusion. The lockdown and social distancing imposed during the COVID-19 pandemic has a significant reducing effect on the incidence of airborne infectious diseases in the population in the absence of effective vaccination.

A clinical case of chickenpox complicated by meningoencephalitis and cerebral edema in combination with a novel coronavirus infection (COVID-19) in a 5-year-old child

The new coronavirus infection COVID-1 9 in children generally proceeds favorably, but in combination with other acute infectious diseases and in persons with background pathology and impaired immune reactivity may pose a particular threat.The article presents a clinical case of chickenpox, complicated by meningoencephalitis and cerebral edema, in combination with COVID-1 9 in a 5-year-old child. Chickenpox was not quite typical: against the background of febrile temperature, there was a scanty spot-papular rash with single vesicles that appeared later, the absence of elements on the mucous membranes and the development of neurological symptoms in the first day of the disease. CОVID-1 9 was characterized by a wave-like course with fever up to 39,1 °C, tonsillitis phenomena and inflammatory changes in the blood test.

On a new SEIRDE o I o epidemic model eventually initiated from outside with delayed re-susceptibility and vaccination and treatment feedback controls

This paper studies a new extended SEIR (susceptible-exposed-infectious recovered) epidemic model which incorporates the contribution of infective contagions to the resident population from infective exposed and infectious outsiders as well as eventual delayed re-susceptibility by partial loss of immunity. It is referred to as a since the dead individuals caused by the disease are defined as a new subpopulation. The potential contribution of the disease propagation of non-resident external infected travellers is considered as well as a re-susceptibility which increases the susceptible numbers and a parallel loss of immunity caused by a potential delayed re-infection. The model is also studied under eventual vaccination and treatment controls each one of them including two additive terms including proportional feedback of the susceptible and infectious, respectively, as well as control actions being independent of the population numbers. The disease-free and endemic equilibrium points are characterized, as well as their dependence on the control gains, and their stability properties are also studied. It is found that they are unique and only one of the two is a global attractor depending on the model parameter values. Typically, the value of the basic reproduction number is crucial to characterize the stability or, alternatively, that of the coefficient transmission rate provided that the remaining parameters are prefixed. The controls are also useful to increase the admissible minimum threshold of the infection force compatible with the stability of the disease-free equilibrium point. Simulation results are given, some of them related to parameterizations of usefulness related to the recent COVID-19, while others to a varicella case study.

A rare case of chickenpox induced myoclonus

In presence of abnormal neurological features, infective etiology should be kept as one of the differential diagnoses. This case report was about 38 years old male patient who presented with fever with blister-like rashes in centripetal distribution over the body and myoclonus. CSF examination showed the presence of varicella-zoster Ig M antibodies. Diagnosis of chickenpox induced myoclonus was made. Appropriate treatment recovered the patient completely. This case report highlighted the clinical spectrum of chickenpox as well as the possible pathogenesis and diagnostic, therapeutic approach of this uncommon entity.

Evaluation of varicella vaccine effectiveness during outbreaks in schools or nurseries by cross-sectional study

ObjectiveThe aim of this study was to elucidate vaccine effectiveness (VE) during varicella outbreaks in schools and nurseries in Japan. MethodsAn outbreak was defined as emergence of three or more cases of varicella within 21 days at the same institute. Clinical information such as varicella vaccination status, and history of varicella was collected. If a child had varicella during the outbreak, information about absences, fever, and disease severity was collected. ResultsFrom September 2018 to January 2020, four outbreaks were reported around our institute from three elementary schools and one nursery. A total of 676 children were analyzed in this study. Seventy-six children (11.2%) were unvaccinated, 309 (45.7%) had received one dose of vaccine, and 291 (43.0%) had received two doses. Most children in Pre-K2 (1–2 years old) to Pre-K6 (5–6 years old), who were the targets of the national immunization schedule, received two doses. Meanwhile, most children older than third grade received single dose. Seventy-five children (11.1%) had varicella. Varicella prevalence from Pre-K5 to the third grade was greater than 10%. The adjusted VEs of single- and two-dose of varicella vaccine were 57.8% and 89.0%. The number of days absent was significantly longer in unvaccinated children than single-dose recipients (P = 0.0145). Unvaccinated children had significantly more severe skin eruptions than single-dose recipients (P = 0.0046) and two-dose recipients (P = 0.0258). ConclusionsAlthough VEs of single-dose varicella vaccination during outbreaks was not high, the VE of two-dose vaccination was similar to that in a previously reported case-control study.

Health Impact and Cost-effectiveness Assessment for the Introduction of Universal Varicella Vaccination in Switzerland.

Varicella, caused by the varicella-zoster virus, is a highly contagious infectious disease with substantial health and economic burden to society. Universal varicella vaccination (UVV) is not yet recommended by the Swiss National Immunization Program, which instead recommends catch-up immunization for children, adolescents and adults 11-40 years of age who have no reliable history of varicella or are varicella-zoster virus-IgG seronegative. The objective of this study was to perform an assessment of health impact and cost-effectiveness comparing UVV with current practice and recommendations in Switzerland. A dynamic transmission model for varicella was adapted to Switzerland comparing 2 base-case schedules (no infant vaccination and 10% coverage with infant vaccination) to 3 different UVV schedules using quadrivalent (varicella vaccine combined with measles-mumps-rubella) and standalone varicella vaccines administered at different ages. Modeled UVV coverage rates were based on current measles-mumps-rubella coverage of approximately 95% (first dose) and 90% (second dose). Direct medical costs and societal perspectives were considered, with cost and outcomes discounted and calculated over a 50-year time horizon. UVV would reduce the number of varicella cases by 88%-90%, hospitalizations by 62%-69% and deaths by 75%-77%. UVV would increase direct medical costs by Swiss Franc (CHF) 39-49 (US $43-54) per capita and costs from a societal perspective by CHF 32-40 (US $35-44). Incremental quality-adjusted life-years per capita increased by 0.0012-0.0014. Incremental cost-effectiveness ratios for the UVV schedules versus the base-case were CHF 31,194-35,403 (US $34,452-39,100) per quality-adjusted life-year from the direct medical cost perspective and CHF 25,245-29,552 (US $27,881-32,638) from the societal perspective. UVV appears highly effective and cost-effective when compared with current clinical practice and recommendations in Switzerland from both a direct medical costs perspective and societal perspective.

Ten-year follow-up on efficacy, immunogenicity and safety of two doses of a combined measles-mumps-rubella-varicella vaccine or one dose of monovalent varicella vaccine: Results from five East European countries

BackgroundWe assessed the 10-year efficacy, immunogenicity and safety of two doses of a combined measles-mumps-rubella-varicella vaccine (MMRV) or one dose of a monovalent varicella vaccine (V) in children from Czech Republic, Lithuania, Poland, Romania and Slovakia. MethodsThis was a phase IIIB follow-up of an observer-blind, randomized, controlled trial (NCT00226499). In phase A, healthy children aged 12–22 months from 10 European countries were randomized in a 3:3:1 ratio to receive two doses of MMRV (MMRV group), one dose of MMR followed by one dose of V (MMR + V group), or two doses of MMR (MMR; control group), 42 days apart. Vaccine efficacy (VE) against varicella (confirmed by viral DNA detection or epidemiological link and clinical assessment) was calculated with 95% confidence intervals using Cox proportional hazards regression model. Immunogenicity was assessed as seropositivity rates and geometric mean concentrations (GMCs). Solicited and unsolicited adverse events (AEs) and serious AEs (SAEs) were recorded. ResultsA total of 3705 children were vaccinated (1590, MMRV group; 1586, MMR + V group; 529, MMR group). There were 663 confirmed varicella cases (47, MMRV group; 349, MMR + V group; 267, MMR group). VE ranged between 95.4% (Lithuania) and 97.4% (Slovakia) in the MMRV group and between 59.3% (Lithuania) and 74% (Slovakia) in the MMR + V group. At year 10, seropositivity rates were 99.5%–100% in the MMRV group, 98%–100% in the MMR + V group and 50%–100% in the MMR control group, and the anti-VZV antibody GMCs were comparable between MMRV and MMR + V groups. The occurrence of solicited and unsolicited AEs was similar across groups and no SAE was considered as vaccination-related. No new safety concerns were identified. ConclusionsOur results indicated that two doses of varicella zoster virus-containing vaccine provided better protection than one dose against varicella and induced antibody responses that persisted 10 years post-vaccination.

Children hospitalised with four common viral diseases showed epidemiological differences but few socio-economic variations.

This study explored the differences in demographic and socio-economic factors between children hospitalised due to four common viral infections. Demographic data were obtained from Statistics Sweden on >3000 children admitted to Astrid Lindgren Children's Hospital in 2009-2014 with rotavirus, influenza, respiratory syncytial virus (RSV) or chickenpox. We compared demographic and socio-economic factors between case groups using logistic regression with rotavirus cases as reference. There were differences in the median age at admission; RSV cases were younger (0.4years), influenza (2.4years) and chickenpox cases (2.7years) older than rotavirus cases (1.2years). RSV, influenza and chickenpox cases lived in families with more children than rotavirus cases. RSV and influenza cases were more likely to have underlying chronic conditions. Mothers of RSV cases were more likely to be born in Sweden. Further socio-economic differences were not robustly confirmed in sensitivity analyses. We found a few differences in demographic factors between children hospitalised with the four common infections, which were mainly explained by the epidemiology and transmission patterns of these infections.

Role of Climatic Conditions on the Incidence of Varicella in an Out-patient Clinic of a Tertiary Care Pediatric Hospital at Dhaka

Background & objective : Chicken pox or varicella is a disease of both tropical and temperate zones bearing a complex-relationship with climatic variables, like temperature, rainfall and relative humidity, wind velocity and so on. As no study has, by far, been conducted to relate its occurrence with these climatic variables in Bangladesh, this study was intended to explore the effect of weather conditions on the incidence of varicella in Dhaka city of Bangladesh.
 Methods: The present cross-sectional study obtained data of 172 varicella cases from the records of the daily register of Out-patient Department of Dhaka Shisu Hospital, Dhaka between January 2018 to December 2019. According to the study protocol a child was diagnosed as having varicella or chicken pox who had a history of short febrile illness accompanied by a pruritic vesicular eruption (on the face and trunk)) of the skin and mucous membranes which ultimate weeps out and crusts. Total number of cases treated monthly at Out-patient Department (OPD) during the period was also recorded. Climatic data were provided by Bangladesh Meteorological Department, which among others, included monthly average temperature, relative humidity (RH) and amount of rainfall or precipitation. While the outcome variable was monthly number of varicella cases, the predictive variables were average temperature, humidity and rainfall during the study period.
 Result: Over 70% of children were 1-10 years old with median age of the children being 5.5 years (range: < 1 month -14 years). Boys were a bit higher (54%) than the girls (46%). A seasonal pattern of chicken pox was seen with clustering of cases between mid-February to mid-April (spring season) with two peaks – one in February and another in April, when monthly average temperature, total rainfall and humidity all were at their optimum. The peak incidences of chicken pox cases during the spring both in 2018 and 2019 as correlated with climatic data of the same period, it is seen that the prevailing weather then was optimum-average temperature was 23°C, average precipitation was 20-25% of the total annual precipitation and relative humidity was around 65%.
 Conclusion: The study concluded that majority of the varicella cases occur under ten years of age and boys are a little more susceptible to have the infection than the girls. A seasonal pattern of chicken pox is clearly seen with clustering of cases between mid-February to mid-April (spring season) with two peaks when monthly average temperature, total rainfall and humidity all are optimally favorable for the multiplication of varicella zoster virus.
 Ibrahim Card Med J 2020; 10 (1&2): 11-17

Case Report: Neonatal Varicella Acquired From Maternal Zoster

The incidence of neonatal varicella has decreased dramatically since the introduction of the varicella vaccination. Although the varicella zoster virus is often associated with a mild infection, it may cause severe morbidity and mortality, particularly in the neonatal period and immunocompromised hosts. We report a case of neonatal varicella acquired from maternal zoster in a mother on biological immunosuppressive therapy. Following the diagnosis, the baby improved on antiviral therapy without any neurological sequelae. This case highlights the limited published data on neonatal varicella following herpes zoster reactivation to inform practice. This includes the role of varicella zoster immunoglobulin in neonates exposed to maternal zoster, the degree of trans-placental immunity and optimum antiviral dosing and duration.

Changes in epidemiological characteristics and sero-prevalence against the varicella zoster virus in school-age children after the introduction of a national immunization program in Japan

ABSTRACT A national immunization program using two doses of live attenuated varicella vaccine was introduced for children aged one to two years in Japan in October 2014. Varicella cases declined after 2014, and immunological status against varicella among vaccinated children changed in post-vaccination era. A retrospective observational study of anti-varicella antibody seroprevalence, varicella vaccination status, and history of varicella among 528 students in the first grade of elementary school was conducted. The percentage of students who received at least a single dose of varicella vaccination increased from 67% (187 of 279 students) in 2007–2008 to 91% (226 of 249 students) in 2017. Students with a history of varicella decreased from 114 of 279 (41%) in 2007–2008 to 48 of 249 (19%, P < .01) in 2017. Among them, the rate of breakthrough varicella after a single dose of vaccine in students with a history of varicella significantly increased from 38% (43 of 114 students) in 2007–2008 to 58% (28 of 48 students) in 2017 (P < .05). The antibody-positive rate significantly decreased from 50% among subjects without varicella zoster who received a single dose (95%CI: 41–58%) in 2007–2008 to 29% (95%CI: 21–38%) in 2017 (P < .01). The antibody-positive rate among students without varicella history who received two doses of vaccine was only 43% (95%CI: 32–55%) in 2017. The number of varicella infections and antibody-positive rate among students without history of varicella who received varicella vaccination decreased after the introduction of a national immunization program.

Seasonal variation and role of meteorological conditions in reported chicken pox cases in a residential hostel of Ramgarh

Background: Chicken pox is an acute, common, and highly contagious disease caused by the varicella zoster virus (VZV). Chicken pox is predominantly a childhood disease characterized by pruritic vesicular exanthema with systemic symptoms such as fever, loss of appetite, and malaise. Primary infection tends to occur at a younger age and is usually benign in immunocompetent children but can be life-threatening in adults and immunocompromised individuals, with an attack rate approaching &gt;85% after exposure. This study attempts to evaluate the trend of chickenpox cases in a residential hostel in Ramgarh.Methods: This was a record based descriptive study done using reported Chicken Pox cases in the OPDs during the period from January 2015 to December 2018. Monthly average for meteorological data (Min and Max temperature, Precipitation and Humidity) for Ramgarh was recorded for the study period. Seasonality and trend was identified for chicken pox cases during this period by plotting the monthly number of clinically diagnosed cases over time period to identify any repeated pattern. Poisson’s distribution was used to estimate association between meteorological variables and incidence of chickenpox cases.Results: Analysis revealed strong correlations (r=0.7553, p&lt;0.0001) between humidity and precipitation. There was a significant correlation between Incidence of varicella and meteorological factors under study (all p&lt;0.05).Conclusions: The findings of this study will aid in forecasting epidemics and in preparing for the impact of climate change on the varicella epidemiology through the implementation of public health preventive measures such as promoting good hygiene practices, temporary closure of educational institutions, active vaccination and campaigns that include press releases and media events to encourage preventive activities.

Study of Some Factors Affecting on the Chickenpox Cases by Using the Partial Linear Regression Model

Chickenpox is classified as a transmission disease, especially young ages from three months to 15 years old. This study clarifies the effect of the area, population, and the number of the health centers on the number of cases of chickenpox disease in the Rusafa district, Baghdad, Iraq. We use the Partial Linear Model (PLM) that divides the independent variables into two parts (parametric and non-parametric). Moreover, choosing the best model that represents data of the chickenpox disease, using criteria (R2, Bic, Aic) from six models. The results of the study show a positive relation between the number of cases and number of health centers.

Varicella zoster immune globulin (human) (VARIZIG) in immunocompromised patients: a subgroup analysis for safety and outcomes from a large, expanded-access program

BackgroundImmunocompromised children and adults are at increased risk for severe disease and death following varicella zoster virus infection. Varicella zoster immune globulin (human) (VARIZIG) is recommended for post-exposure prophylaxis to prevent or attenuate varicella infection in high-risk individuals.MethodsAn open-label, expanded-access program provided VARIZIG to high-risk individuals exposed to varicella or herpes zoster. Immunocompromised participants were stratified by type of immunocompromising condition (“oncologic immunodeficiency”, “primary immunodeficiency”, “solid organ transplant” [SOT], “hematopoietic cell transplant” [HCT], and “other”). Patient characteristics, type of exposure and varicella outcome, and safety data were assessed.ResultsThis analysis included 40 adults (primary [n = 6] or oncologic [n = 10] immunodeficiencies, history of SOT [n = 5] or HCT [n = 6], and other [n = 13]), and 263 children (primary [n = 13] or oncologic [n = 152] immunodeficiencies, history of SOT [n = 36] or HCT [n = 17], and other [n = 45]). Among adults and children, 48% vs 72% were exposed to varicella, 38% vs 16% were exposed to herpes zoster, and 15% vs 12% had an unspecified exposure. Overall incidence of varicella infection in adults after VARIZIG use was 6%; incidence of varicella infection in children after VARIZIG use was 7%. Similar rates were noted in each subgroup. Most cases of varicella were mild, with two children developing > 100 lesions and no cases of varicella-related pneumonia or encephalitis. Varicella-related hospitalizations occurred primarily in children with oncologic immunodeficiencies. One serious adverse event (serum sickness) was considered related to VARIZIG and occurred in a child with oncologic immunodeficiency. There were no varicella- or VARIZIG-related deaths.ConclusionsThese data indicate that VARIZIG may reduce severity of varicella in immunocompromised children and adults.Trial registrationThis study was retrospectively registered with the public clinical trial identification NCT00338442 at https://www.clinicaltrials.gov on 20 June 2006.

INTERNET BASED DATA AS A POWERFUL TOOL FOR TRACKING INFECTIOUS DISEASE DYNAMICS

Purpose: Digital epidemiology (using Internet data as an epidemiological tool) is one of the most concurrent and novel approaches in the field of infectious disease tracking. We aimed to see if the disease-related information seeking via one of the most popular search engine (Google) correlates with the real varicella epidemiology in Bulgaria. Material/Methods: We compared the relative search index obtained by Google Trends with a keyword ‘varicella’ and the real incidence data for 2016-2018 in Bulgaria. Correlation analysis and t-test were used to see for association and difference in the means. Additionally, we summarized what type of information people find when searching for ‘varicella’. Results: Dynamics of Google Trends with search term ‘varicella’ followed almost exactly the real dynamics of reported varicella cases in Bulgaria (Pearson’s correlation coefficient of 0.85). The seasonality and the regional spread of varicella infection were also confirmed by the digital epidemiology (Pearson’s correlation coefficient between the search index and the monthly cases was 0.93 and between the search index and the individual district incidence was 0.35). The majority of the information found by people during the seasonal varicella outbreaks was scientifically relevant and correct. Conclusions: Digital data received by non-epidemiological methods could be successfully used to study varicella dynamics, as high correlation exists between the data collected via the traditional methods and via the new, digital methodology.

Global stability of varicella model

Varicella is a disease caused by the varicella-zooster virus. This disease is common in children under 10 years of age and is not a fatal condition. However, some cases of varicella in adults are more dangerous because they can cause pneumonia. Here, discussion about analysis of varicella epidemic model is presented. This model is expressed in the form of 6th order differential equation with state variables as follows susceptible, exposed, infected, quarantine, recovered, and vaccination. Apart vaccination and isolation intervention, this model also consider disinfectant spray an¡d ventilation. Our analysis shows that varicella dynamic behavior depends on the basic reproduction number (R 0). The model has two equilibria, namely, free disease and endemic equilibria. By using the Lyapunov function, we demonstrate that when R 0 ≤1, disease-free is globally asymptotically stable, and when R 0 > 1 disease-free becomes unstable while endemic is globally asymptotically stable. This results indicate more effective each intervention, the better the control of varicella.